GENUS II. LEPAS. 45 



ture destined for the residence of the animals. Most of the 

 shells in this genus are very porous ; but the pores in this divi- 

 sion are so large that w^e may rather call them cells, as may be 

 seen in pi. 1 . /. 6, where the underside of Lepas Diadema is 

 represented. 



There are also a few species of a very different form and 

 texture ; these are attached to other substances by means of a 

 cartilaginous tube, which is sometimes of a considerable length ; 

 the shells themselves are very much compressed or flattened 

 sideways (/»/. 1. /, 2), as in Lepas anatifera; the number of 

 valves vary in the different species from five to thirteen or 

 more. These have been separated from the rest by several 

 authors, particularly Dr. Pulteney and Mr. Montagu, wiio 

 have formed of them a new genus called Lepas : to the re- 

 mainder they give the name of Balanus. 



Linnaeus, in the twelfth edition of Sy sterna Naturce, describes 

 only 10 species in the whole; Gmelin has added 18, and 

 Dr. Turton 4, making together 32; but it is supposed that 

 more than double this number are now known. 



Lamarck has divided this genus into four, as follows* : 

 Balanus, a conic shell, truncated above, fixed by its base, 

 without a cartilaginovis tube, and composed of six valves, 

 articulated by the sides and by their lower edge. The 

 aperture closed by a four-valved operculum (see Lepas 

 tintinnabuhnn Linn, pi 1. /. 3 and 5). 



* See Parkinson's Organic Remains, vol. 3. p. 239 and 240. 



